For some time it has been known to provide a packaging film which contains silicone oil, in an outer film layer and/or an inner film layer. Silicone oil has been sprayed onto the surface of a film, as well as extruded in admixture with one or more polymers which make up the film, including polymer making up an outer layer of a multilayer film. The silicone oil has been used in combination with antiblocking agents, such as particulate silica, to provide a film having a desired coefficient of film-to-metal slip, as well as imparting desired antiblocking characteristics to the film.
It has been discovered that a film having two outer layers, each of which comprises 72.5 weight percent ethylene/propylene copolymer, 15 weight percent polybutylene, and 12.5 weight percent of a masterbatch comprising about 90 weight percent polypropylene (based on masterbatch weight), 4% inorganic antiblock, and 6% of a blend of fatty acid amides (hereinafter, "amides"), if used in a horizontal-form-fill-and-seal operation ("HFFS"), or vertical-form-fill-and-seal operation ("VFFS"), results in an unacceptable amides/antiblock buildup on the machine surface of the HFFS machine, or VFFS machine, because the amides/antiblock buildup sluffs off into the product, and/or hardens and damages the film. The amides/antiblock buildup is caused by the amides, which are extruded in admixture with the polymer of the surface layer, blooming to the surface of the film, in an amount thick enough to result in the buildup on machine surfaces. The antiblock particulates on the surface of the film also accumulate on the machine surfaces, together with the bloomed amides.
However, the fatty acid amides are present in order to provide the film with a desirable film-to-film coefficient of friction, so that packaged products slide freely when in contact with one another. This is desired in order to facilitate alignment of packaged products for the bulk packaging thereof, for example in boxes, as well as providing a desired low film-to-equipment coefficient of friction.
Thus, it would be desirable to provide a film which exhibits a low film-to-film coefficient of friction, as well as a low film-to-equipment/metal coefficient of friction, without buildup of fatty acid amides/antiblock on equipment/metal, and particularly without buildup and subsequent sluffing off into the product being packaged in the film. In order to accomplish this result, it would be desirable to reduce or eliminate the presence of fatty acid amides on the surface of the film, while providing a desired low film-to-equipment coefficient of friction, and while providing a desired low film-to-film coefficient of friction.